New Central Subway construction is beginning soon around Union Square.

Beginning Monday, July 30, Stockton Street between Ellis and Geary streets will be closed to all vehicles except emergency vehicles to accommodate construction of the Central Subway tunnel and Union Square/Market Street Station. To facilitate local access to Union Square, Grant Avenue between Geary and Sutter streets will be converted into a two-way street starting Saturday, July 28.

The partial closure of Stockton Street will remain in effect throughout the duration of Central Subway construction except during the annual holiday construction moratorium. From Thanksgiving to New Year’s Day, no Central Subway construction will occur around Union Square, and Stockton Street will be reopened to traffic. Grant Avenue between Geary and Sutter streets will remain a two-way street during the holiday moratorium.

Variable message signs and detour signs will be in place to direct traffic to the detour routes shown on the map below.

This map shows two suggested traffic reroutes: local access to Union Square via Grant Avenue and a detour around Stockton Street for travel to SoMa and I-80.

In addition to the traffic modifications on Stockton Street and Grant Avenue, Ellis Street between Stockton Street and the Ellis Garage will be closed to westbound traffic. One lane will remain open to eastbound traffic. Vehicles exiting the garage will be able to turn left or right onto Ellis Street.

Tunnel preparatory construction, including ground-stabilization work, called jet grouting, and installation of below-ground walls, called headwalls, will begin on and around Stockton Street after the traffic modifications go into effect. Construction of the Union Square/Market Street Station is slated to begin early next year.